Sun was killed by the confluence of a poorly timed loan and the GFC. Their revenue/cash reserves were insufficient to cover payments on loans taken at the peak before the crash. When GFC happened, their primary Wall Street customers suddenly turned cost conscious. I think that if they had negotiated slightly better terms on the loan they'd still be around today.
That sounds like a final straw; if they'd been well managed and healthy, would that have necessarily been a killing blow (I don't know about those details of their fall, just the decline that preceded it and made it inevitable).
